1. Field of the Invention
The present invention relates to a sterilizing method. More particularly, the present invention relates to a method for sterilizing biological materials employing ozone.
2. Description of Related Art
Typically, biological materials, which may refer to materials existing in or derived from living organisms, substantially comprise components, such as amino acids, peptides, proteins, polysaccharides and so on, directly extracted from microorganisms, animals or plants. As the biological material itself possesses excellent biocompatibility, it has potential in medical applications, for example, wound dressing and scaffold for tissue engineering, as well as in pharmaceutical and cosmetic industries. The biological materials for human or living organisms must be subjected to a strictly sterilizing procedure. However, most of the biological materials are susceptible to high temperature sterilization, and they are also liable to be denatured. The option of methods for sterilizing the biological materials is very restricted. Thus, the application of the biological materials is presently focused on how to achieve the sterilizing effect and to save the bioactivity of biological materials, rather than destroying their properties.
There are several methods of sterilizing biological materials as follows. (1) Sterilization with 75% ethanol: The biological material is immersed in 75% ethanol, and it must be reserved and delivered in moist state. However, the bioactive components are liable to be denatured in such moist state. Moreover, it is not sure whether ethanol is completely removed from or remains in the biological material when rinsing it before use. (2) Sterilization with gamma (γ)-irradiation as disclosed in U.S. Pat. No. 5,485,496, and Taiwan Pat. Nos. 145,942 and 115,972: This method is applied commonly, which employs γ-ray to irradiate the biological materials. However, the energy of the γ-ray is so high that some chemical structures of the biological material are destroyed, resulting in weakening the mechanical strength of the biological material. In addition, the irradiation is hazardous to human so that it has to be operated in a specific place, resulting in inconvenient usage. (3) Sterilization with ultraviolet light as disclosed in Taiwan Pat. No. 474,828: This method employs ultraviolet light to irradiate the biological materials for sterilization. Nevertheless, the ultraviolet light penetrates to minimal distances and only the surfaces of the biological materials can be sterilized. Thus, the ultraviolet light is unavailable to sterilize the biological materials mostly with three-dimensional shape and opaque property. (4) Sterilization with chemical reagents as disclosed in U.S. Pat. Nos. 5,460,962 and 6,096,266, as well as Taiwan Pat. Nos. 310,308, 241,193 and 149,465: This method is accomplished by adding chemical bactericides into the biological materials. However, the chemical bactericides are toxic and difficult to be removed, so it is applied in fewer fields. (5) Sterilization with high temperature and high pressure (autoclave) as disclosed in Taiwan Pat. No. 443,932: The autoclave method results in the denaturation of biological materials, even completely losing their bioactivity. In sum, the aforementioned methods have respective drawbacks, which often cause biological materials to change in chemical structures and properties, resulting in biocompatibility and applicability.
Ozone is typically applied in surface modification of polymeric biomaterials. Ozonization refers to generate activated peroxide on the surface of the biomaterial, and it further induces graft copolymerization with some functional groups on the biomaterial, as well as degradation in aqueous environment. For the use of sterilization, ozone is usually applied in sterilization of general instruments as disclosed in U.S. Pat. No. 5,788,941 and Taiwan Pat. No. 061,995. This method is accomplished by placing the object into an ozone-containing environment. In general, a biological material has certain aqueous content and even exists in a solution state. As such for the aqueous biological material, the aqueous content existing in the sample may react with ozone gas, resulting in changes of chemical functional groups inside the biological material, and even micro-changes inside the structures of the biological material, such as polymerization, degradation and so on, thereby affecting physiochemical properties of the biological material. On the other hand, as such for the biological material in solution state, ozone dissolved in the solution may be insufficient to achieve a desirable sterilizing effect. If ozone is directly introduced into an aqueous solution, the same problem caused by ozone sterilization to the water-containing biological material will happen.
For the foregoing reasons, it is necessary to develop a method for sterilizing biological materials, while maintaining bioactivity and structure thereof, such that the method can be widely applied to the biological materials.